1. Field of the Invention
The present invention relates generally to data storage devices such as HDDs (hard disc drives), and more particularly to retrying of a data read within a data storage device with adjustment of read timing depending on eccentricity of a disc.
2. Description of the Related Art
A hard disc drive (HDD) is a common data storage device within a computer system. The HDD reads/writes data from/to a disc using a magnetic head. For higher-capacity, higher-density, and smaller-size of the HDD, recording density is increased on the disc in both a rotational direction of the disc (i.e., BPI—bits per inch) and a radial direction of the disc (i.e., TPI—tracks per inch). With such higher density, a mechanism for more accurately controlling the magnetic head is needed.
In addition, with such higher recording density and decreased size of the HDD, characteristics of the HDD mechanisms and circuits change, resulting in error during a data read operation. When such an error occurs, a retry process is performed. Typically upon detection of an error during a data read operation, parameters associated with an off-track read or a data read operation are changed, and the data read operation is repeated with such changed parameters.
If the error recurs, the parameters are changed again, and the data read operation is again repeated with the further changed parameters. Such change of the parameters and data read operation with the changed parameters are repeated up to a predetermined maximum number of times.
If the HDD is subjected to external impact, disc slip occurs. Such disc slip results in disc eccentricity. When a data read operation is performed with such a disc slip, the retry process may be performed too many times because of the disc eccentricity from the disc slip, resulting in failure of the data read operation.